This invention relates to monitoring vital signs, and more particularly to monitoring of breathing and/or heart rate via radio reflections.
The monitoring of vital signs (e.g., a human heart rate and breathing rate) of subjects without requiring that a monitoring device be in physical contact with the subjects is an active area of research. Contemporary approaches for non-contact vital signs monitoring can be divided into two areas: vision-based techniques and wireless techniques.
For vision based techniques, advances in image processing have allowed researchers to amplify visual patterns in video feeds (e.g., color changes due to blood flow) to detect breathing and heart rate. Such video-based techniques have drawbacks since they require the subject to face the camera and do not work properly when the subject turns away from the camera or is outside the camera's field of view.
For wireless techniques, advances in wireless transmission systems and signal processing have enabled researchers to monitor vital signs by analyzing characteristics of wireless signals that have reflected off of the subject. Some examples of wireless vital sign monitoring techniques utilize Doppler radar, WiFi, or ultra-wideband radar. One challenge in using wireless signals to monitor vital signs is that any motion in the environment affects the signal. Since breathing and heartbeats are minute movements, they can be easily masked by interference from any other source of movement in the environment. Furthermore, the presence of multiple users, even if the users are stationary, prevents systems from operating correctly since the wireless signal is affected by the combination of their vital signs, making it difficult to distinguish the vital signs of each individual. Conventional approaches deal with this problem by ensuring that there is only one source of motion in the environment: namely, the vital signs of the monitored individual. Hence, the experimental setups of the past approaches typically require a single person to lie still in close proximity to the device.